I didn’t realize this either. I was looking for it in the UI a week or two ago and didn’t find it because the tooltip doesn’t show the instructions for Ctrl+Click unless you hover over a block with a color or opacity set. I had hovered over a nearby block’s title and the instructions just said to double-click. Bleh!
Also, these instructions (double-click, ctrl+click) are short enough they should be included in the legend shown by clicking the “?” button at the bottom right.
Ah, but there is no way to set the color or opacity for multi-selected blocks; only the block whose icon is double-clicked gets modified. The multi-selection can only be used to change visibility. Which seems inconsistent.
Instead of using click to enable/edit (which is unusual) and Ctrl-click to reset and disable (which is not discoverable) we could use a context menu with two options: Enable (or Edit) and Reset. This context menu can also be documented in the tooltip. I understand that you show if a property is overridden or not by enabling/disabling the control.
Context menus are not really discoverable, either.
If we are going to have a popup to edit the color or opacity, that popup should just have a “Reset” (to prior value) and/or “Clear” (of any setting) button on it that is enabled when the property is already set and disabled otherwise.